a. Field of the Invention
The invention relates to the production of a thin stock sheet material and in particular to continuous methods of producing thin, reinforced sheets of plastics which flow before setting but not after.
b. Prior Art
The class of plastic materials which includes thermosetting plastics and catalyst cured plastics are materials which readily flow before setting, but not afterwards. This class includes materials such as epoxy, melamine formaldehyde, melamine phenolic, phenolic, polybutadiene, thermosetting polyesters, thermosetting polyimide, polyurethane, silicone and urea. For convenience, this class will be termed "fluid-setting plastics" for this application.
Previously, fluid-setting plastics have been sold primarily as cast pieces. This implies high cost because of batch processing. Fluid setting plastics tend to have low tensile strength when cast in thin sheets. This has limited the ability of manufacturers to produce fluid-setting plastics in large thin sheets.
One approach in solving the problem of low tensile strength is to add reinforcing fibers to the material. Cast epoxy reinforced with glass or graphite fibers is a well known high strength material. Another approach is to form a laminate which reinforces the low strength fluid setting material. Many epoxy laminates are known.
An object of the invention was to devise a method for making reinforced fluid setting plastic sheets.